Kombu is the collective name for the Laminaria species of brown seaweeds. Also called kelp, kombu is found mostly in the North Atlantic and Pacific oceans. Mineral-rich kombu, which contains high amounts of iodine, potassium, calcium and iron, can cause a wide range of reactions and side effects, both positive and negative.
Kombu’s primary mineral is iodine, a natural, nonmetallic chemical. Doctors prescribe iodine-based medications to boost thyroid hormones in people with malfunctioning thyroid glands. In healthy people, too much iodine can overstimulate the thyroid, resulting in nervousness, heart palpitations, sleeplessness and irritability. A Japanese study found that eating kombu daily for two months to three months substantially increased thyroid levels, yielding higher than normal hormones in adults. Hormone levels returned to healthier rates a week to a month after stopping kombu ingestion. Some Japanese cooks recommend soaking kelp in water for 30 minutes to remove iodine. People with seafood allergies are especially sensitive to excess iodine.
Kombu contains the amino acid glutamate, the key ingredient in the preservative monosodium glutamate. For people sensitive to MSG, kombu can cause reactions including headaches, nausea, irregular heartbeats and difficulty breathing. Other symptoms include tingling, numbness or a burning sensation in the neck, arms and chest. In extreme cases, anaphylaxis, or sudden cardiac and respiratory arrest related to an allergic reaction, can result from glutamate exposure.
Asian health professionals use some kombu varieties to dilate the cervix or induce labor. Kombu can also affect fetal heart rate. Researchers have not closely studied the effect of kombu on women and fetuses during early pregnancy, so most doctors advise expectant women to avoid eating kombu to be on the safe side.
Kombu’s mineral properties make it a healthy dietary addition for people with normal thyroid function and no seafood sensitivities. Its iron can help hemoglobin production. In people with low thyroid function, kombu offers a natural source of hormone-boosting iodine. The potassium in kombu can ease symptoms of fibromyalgia and fatigue. Kelp is also a good source of the sleep-inducing hormone melatonin. The algin in kombu is concentrated in bulk laxatives, and eating a smaller amount can provide a gentler boost to regularity. Kombu has also been linked to anticoagulant activity and lower blood pressure. Kelp can even help treat radioactive overexposure.